import org.junit.Test;

public class AbstractTest {
    public static void main(String[] args) {
        Circle0 circle = new Circle0();
        getArea(circle);
    }

    public static void getArea(Geometry g) {
        System.out.println(g.findArea());
    }

}

class Circle0 extends Geometry {

    private double radius = 1;

    @Override
    public double findArea() {
        return Math.PI * radius * radius;
    }
}

abstract class Geometry {
    public abstract double findArea();
}